STEWART KNOW-IT-ALL: James asks, why do leaves change color?

Leaves change color in the fall as a result of the trees reaction to fewer hours of daylight and cooler temperatures. During this period, trees respond by producing less and less chlorophyll. Eventually the chlorophyll disappears and the brilliant fall colors appear.

Leaf color comes from three pigments which are natural substances produced by cells. They include chlorophyll, carotenoid and anthocyanin. Of the three, chlorophyll is the most important. Without chlorophyll, trees wouldn’t be able to use sunlight to produce food.

Carotenoids create bright yellows and orange colors. Anthocyanin is responsible for the color red.

The yellow, gold and orange colors created by carotenoid remain fairly constant from year to year. Their color isn’t affected by changes in weather nearly as much as the red colors that can seem brighter and more spectacular in some years.

The amount of rain in a year also affects fall colors. A severe drought can delay the arrival of fall colors by as much as a few weeks. A warm, wet period during the fall will lower the intensity or brightness of fall colors. A severe frost will kill the leaves, turning them brown and causing them to drop early.

When leaves change color from green to yellow, bright orange or red, you will know that trees are beginning their long winter’s rest.